1. Field of the Invention
The present invention relates to the polyphenylene sulfide resin compositions which are excellent in weather ability and whose supersonic and molding welds are increased in strength, and also relates to their moldings.
Polyphenylene sulfide resins are substantially excellent in heat resistance (incl. short- and long-term characteristics), chemical resistance, flame resistance, size stability and other properties. Being superior in moldability also, they are injection molded for so-called engineering purposes in electric, electronic, automotive and other industries. Their demand is therefore forecast to increase further in future and they are expected to become used to produce films, fibers and other extrusion moldings.
2. Description of the Prior Art
Polyphenylene sulfide resins thus have a variety of features. It is however their substantially-only defect that they are not excellent in ultraviolet ray stability and weather ability. Therefore, they are not suitable for such materials used outdoors as extrusion moldings, films, fibers and others, as well as for indoor strong ultraviolet ray exposition purposes. For example when extrusion moldings, films and fibers are used outdoors, the surface of moldings becomes rough, causes microcracks, considerably decreases in mechanical strength, changes dark brown or decreases in transparency. The defect of polyphenylene sulfide resins being inferior in weather ability has hitherto been known so much efforts have been paid to obviate them in a variety of sectors. It is included among their major features that they are very excellent in heat resistance. This defect always requires molding temperature to be raised to a considerably-high value. Its standard ranges between about 300.degree. and 360.degree. C. Those concerned have a common knowledge that it is necessary for the improvement in characteristics to add suitable additives to so-called universal thermoplastic whose molding temperature is below 300.degree. C. and universal engineering resins. The improvement in weather ability of polyolefins for example that is included among the purposes of the present invention is made by adding ultraviolet absorbents and/or oxidation preventives. Polyphenylene sulfide resins however require molding temperature. The additives for the improvement in characteristics are required to have the resistances to more than 350.degree. C. heat i.e. neither sublimate nor vaporize and do not change in quality due to deterioration at these temperatures. At present no more than 350.degree. C. heat resistant ultraviolet ray absorbents have been put on the market and published although makers continue research efforts. Few patents or literatures references have been published as regards the improvement in weather ability of polyphenylene sulfide resins. Only Japanese Unexamined Patent Publication No. 100139/1984 can be cited in this connection. The purpose of the present invention is to provide the resin compositions composed of polyphenylene sulfide and a carbon black with a mean particle diameters less than 30 m. The latter's addition for the improvement in weather ability is a know technique in plastic industry. It applies to polyphenylene sulfide resins. The description of the embodiments of the present invention purports that they are improved in weather ability by adding 10% by weight, a considerably-larger amount than that used for ordinary blacking, of carbon black. The inventors added 0.5% by weight, the ordinary addition amount for the blacking of polyphenylene sulfide, of carbon black for comparison. As the result, however, it was found that the weather ability improvement effect of the polyphenylene sulfide resin obtained thereby is too small for standing outdoor use. It is aggreeable in view of this fact that several to 10% by weight order addition ratios are necessary to attain the weather ability standing outdoor use as stated in connection with the embodiments of Japanese Unexamined Patent Publication No. 10013/1984.
Besides cited among the preferable characteristics of polyphenylene sulfide resins is the strength of supersonic and molding welds. It can neither be said to be considerably smaller than that of other resins nor fatally defective. The insufficient strength causes design restrictions, cracks in parts assembling process and other troubles. It is a fact that these obstruct the increase of the purposes of polyphenylene sulfide resins. The study for their increase in strength is earnestly being carried out by various companies.
As stated above, the prior art described in the patent with Japanese Unexamined Patent Publication No. 100139/1984 for example lays down the following restrictions for successfully raising the weather ability that can be said to be the substantially-only defect of polyphenylene sulfide resins. Namely:
(1) They can only be used for black colored goods but not for films that require transparency. PA0 (2) They considerably lower the electric characteristics that are included among the features of polyphenylene sulfide resins since carbon black being inferior in insulation performance is added in great quantities. PA0 (3) Their supersonic and other welds are not increased in strength.